A Study of the Characteristics of the Muang Ngam River Mackenzie Nicholas Wallace 2064 TABLE OF CONTENTS 1. Aims 3 2. Study Location Details 3 3. Background information 6 4. Hypotheses 8 5, Methodology 8 6. Data Presentation and Analysis 10 7. Conclusion 13 8. Evaluation 13 9. Bibliography 14 10. Appendix 14 2 1. Aims 1. How do the characteristics of the Muang Ngam River change with distance downstream? 2. Do human activities affect the physical characteristics of the Muang Ngam River? 2. Study Location Details During the That On field trip, we studied river processes on the Muang Ngam River. The study location was positioned in the far northern regions of Chiang Mai and Chiang Rai, this was also near the Myanmar border (illustrated below in maps 1, 2, and 3). Fig 1. Map of Northern Thailand Showing the study sights 3 Fig 2. Map of Chiang Mai Province showing the study sights Fig 3. Map of That On showing the study sights riverside locations 4 Study Location 1(Red): At the first location, we were located at the upper course of a river where there was a cliff on one side and a flat area on the other which had many trees and other forms of vegetation. There were lots of small rocks and pebbles which obstructed the flow of the river causing it to reduce velocity further down the stream. Site Location 1 Location 2 (Green): At the second location, we were located at the middle course of the river where a few meanders were forming. A cafe was built next to the river where a significant meander had formed. To slow the rate of erosion, the owners had placed a boulder on the river bank below to stop the river from eroding the foundation of the building. They also built a small dam to slow the flow of the river, reducing the erosion rate even more. Site Location 2 Location 3 (Purple): At the final location, we were located at the lower course of the river where the width was 6 metres. On one side there was lots of farming and agriculture whereas on the other side, there was a river bank consisting of sand and small pebbles which was 3 to 4 metres wide and had a road around 2 metres above which followed the contour of the river. 5 Site Location 3 3. Background information 3.1 The Bradshaw Model The Bradshaw Model is layered in triangles which shows how the features of a river change further down the stream. The changes consist of channel depth, channel width, mean velocity, discharge, and volume of load. This Model suited our study because we were able to compare the differences from upstream where the load particle size, channel bed roughness, and gradient of the stream were all larger, rougher, and steeper to downstream where the load sizes were a lot smaller, the channel bed roughness was smoother, and the gradient was flatter then steep. We also found that downstream was more shallow and much wider than upstream, the mean velocity was slower, there was very little discharge, and the volume of load had decreased significantly. Diagram of the Bradshaw Model 6 3.2 River Processes The three main and most important types of processes that take place in a river are erosion, transportation, and deposition. ○ Erosion - the breaking down of material over time. There are four types of erosion, attrition (rock on rock), hydraulic action (pressuring), corrasion (abrasion), and solution (corrosion). ○ Transportation - the movement of an object. There are four types of Transportation in rivers, suspension (fine, light material carried by the river), traction (large rocks rolling along the river bed), solution (minerals dissolved into the water), and saltation (small stones bouncing along the river bed). ○ Deposition - the deposit point of a moving object. In slightly more detail, a river drops its load when the speed of the river decreases. The heavier material is deposited first, whilst the finer material is carried farther down the river. At each study site, we could see how these processes had affected the river and the river bed. At site 1 we could see that the cliff on the right was being eroded by the river due to corrosion. Site 2 showed signs of transportation where solution was taking place and at site 3 we could see signs of deposition where the river had deposited material due to the decreased river speed. 3.3 Long Profile The long profile of a river is relevant because it shows the changes in elevation along its course. It helps us understand the river's gradient, flow, and potential hazards. Diagram of Long Profile In studying three site locations and gathering data, we were able to study the river processes and demonstrate the long profile of the Muang Ngam River. At site 1, we were able to see significant deposition. Site 2 had evidence of erosion. Site 3 had evidence of both deposition and transportation. 7 4. Hypotheses 1. River discharge will increase downstream. I believe this is true because according to the Bradshaw model, river discharge is the volume of water that passes through a selected area at a specific time. As tributaries join the main channel the amount of water will increase and the channel becomes wider and deeper. 2. Bedload will become smaller and smoother with distance downstream. I believe this is true due to the erosion processes such as attrition. 3. The occupied channel width will increase downstream. I believe this will occur as we are starting at a source of a tributary leading towards the larger Kok River. This will be an example of the long profile of a river system. 5. Methodology 5.1 Data Collection ● River Velocity ○ Measuring the five-metre distance in the river channel and releasing a tennis ball from point A (o metres) to point B (5 metres), we then measured the time it took for the ball to travel the measured distance. Once we got the results we divided the distance the ball travelled by the average time to find the velocity of the river in metres per second squared. ● River Channel Cross Sectional area ○ The cross-sectional area is the width of the river multiplied by the average water depth. To find the width of the river, we used a measuring tape to measure the width and a metre ruler for the average water depth and took 1 measurement every 5cm to 1m. ● River Discharge ○ To calculate the river discharge, you must calculate the river's cross-sectional area and then multiply the result by the velocity. ● Bedload size and shape ○ To measure the bedload size you must collect multiple pebbles from the river bed and measure the height, width, and depth of each one using callipers. For the bedload shape, use the pebbles collected prior and compare them to the Powers Index of Roundness to get the average bedload size and shape. We used random systematic sampling to gather our materials. Random systematic sampling means depending on the width of the river, the number of stones to collect either increases or decreases. 8 ● River Gradient ○ River gradient is referred to as the slope of a river, it is the vertical drop over a horizontal distance. It is measured by placing the bottom of two poles on the surface of the river at 2 different locations 5 metres apart and using a clinometer to measure the angle from the top of the first pole to the top of the second. 5.2 Equipment ○ ○ ○ ○ ○ ○ ○ ○ Callipers Metre ruler Tennis ball The Powers Scale of Roundness Clinometer Tape Measure Pipes Stopwatch 9 6. Data Presentation and Analysis Cross-Sectional Area (Site 1) This graph shows that there are two slightly deeper parts of the river at the first site, the first drop being around 0.4 metres in and 0.13 metres deep, and the second drop being around 1.1 metres in and 0.07 metres deep. The deepest part of this section of the river was 0.13 metres and the shallowest part was 0.04 metres. There are no anomalies in this reading. This is what we were expecting because the river wasn't very wide and not abnormally deep. Cross-Sectional area (Site 2) This graph shows that there was one major drop in this part of the river, it stretched from 1.4 metres to 4.8 metres where the river bed reached the river surface. The deepest part of the river was 0.6 metres whereas the shallowest part was 0.02 metres at the beach of the river. There are no anomalies in this graph. 10 Cross-sectional Area (Site 3) This graph shows the river didn’t have any major drops or deep parts except for the bank which stopped at a cliffside which had farmland on top. Halfway through the river at 3m, the river was 10cm deep and at 6m the river was around 15cm until it rose into a beach and farmland. Bedload Shape Graph 11 This graph shows us that the further downstream you go the more round your bedload shape will be. At site 1, the bedload is more angular and sub-angular. At site 2 they’re subrounded and sub-angular. At site 3 they’re mostly sub-rounded and few are sub-angular. Average Velocity Average velocity is calculated by dividing the distance taken by travel time using the measuring tools listed above. The results are listed in the graph below. These were then used to calculate the river discharge River discharge is calculated by multiplying the cross-sectional area by velocity. The cross-sectional area was calculated by multiplying the average depth by the width of each site. The graph above illustrates our results. 12 7. Conclusion 1. Using this data in reviewing my hypothesis, I reject hypothesis 1 because both sites 2 and 3 have a lower river discharge than site 1. This is unexpected and does not support my hypothesis. I am not sure why this would occur. 2. Using data from my bedload analysis, I am accepting my hypothesis because I found the bedload did get smoother and rounder the further downstream proving my hypothesis. This is evidenced by the greater quantity of semi-rounded rocks at site 3 than at sites 2 and 1 which shows attributable to the erosion process attrition. 3. In an analysis of width amongst the three sites, I accept my third hypothesis that the occupied channel width did increase downstream. This is proven in my cross-sectional area graphs which show an increase in width from site to site. 8. Evaluation As a group, we worked effectively to gather the data recorded for the study. We each took a component of measurement and worked on them simultaneously using different tools to collect all the data. The key tools for data collection were confusing at first and took some time to get used to. We had some time when we were able to practise before recording our data so this did not harm our results. The methods we used worked well because the equipment we used was in good condition which gave us fairly accurate measurements. As seen in our data there were no anomalies or outliers for us to discount. It would have been useful in comparison if we had more data for the cross-sectional area at sites 1 and 2 because this would have given us more accurate results when plotting our data on a graph. For the bedload measurements, it would have been useful if we had more study locations to compare the bedload shape. For instance, one additional site is located further up from site one and another is located further down from site 3 toward the mouth of the river. Which ultimately would leave us with five study locations and an expected increase in the range of bedload data. In the future, it would be interesting to see how much the rivers and study locations have changed. This could include visiting in a different season or after a specific amount of time to be able to compare with our current data. It would also be interesting to interview the locals about irrigation usage and the impact this has on river flow. 13 9. Bibliography https://mrgeogwagg.wordpress.com/2015/08/26/river-processes-and-pressures/ Bradshaw Model Diagram (Sourced, 13/2/23) https://www.twinkl.ie/illustration/long-profile-off-a-river-geography-rivers-diagram-secondary Long Profile Diagram (Sourced, 13/2/23) 10. Appendix No Additional Data was included for adding in the appendix. 14
